Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02696832 2011-12-08
DESCRIPTION
FUEL CELL WITH SHIFT EXTENDED MESH
TECHNICAL FIELD
[0001]
The present invention relates to a fuel cell.
BACKGROUND ART
[0002]
In a fuel cell, a cell (single cell) serving as a minimum unit is formed by
stacking a plurality of cell constitutional members, and by forming a stack
structure in
which a plurality of cells are stacked, a required voltage is secured. A
separator
constituted by a plate-shaped component is used in the stack structure as a
member that
is positioned on an outermost layer of each cell to separate each of the cells
in the stack.
Further, the separator functions to supply a fuel gas to an anode side and an
oxidant to a
cathode side, carry electricity generated by the cell, discharge generated
water
generated in the cell, and so on.
[0003]
FIG. 18 shows an example of the cell structure of a polymer electrolyte fuel
cell.
A cell 10 is structured by disposing a membrane electrode assembly 12 ("MEA"
hereafter) in a central portion of the cell 10 in a thickness direction, and
disposing a gas
diffusion layer 14 (anode side/cathode side gas diffusion layers 14A, 14C), a
gas flow
passage 16 (anode side/cathode side gas flow passages 16A, 16C), and a
separator 18
(anode side/cathode side separators 18A, 18C) on either side of the MEA 12.
Note that
a structure formed by integrating the MEA 12 and the gas diffusion layer 14
may be
known as a MEGA (Membrane Electrode & Gas Diffusion Layer Assembly).
In the structure of the cell 10 shown in FIG. 18, in which the gas flow
passage
16 is formed as a separate structure to the separator 18, the aforementioned
functions of
the separator are secured by employing an expanded metal, for example, as a
structure
for forming the gas flow passage 16 (see Patent Documents 1 and 2, for
example).
CA 02696832 2010-03-03
2
[0004]
Patent Document 1: Japanese Patent Application Publication No.
JP-A-2005-310633
Patent Document 2: Japanese Patent Application Publication No.
JP-A-2002-198069
DISCLOSURE OF THE INVENTION
Problem to be solved by the Invention
[0005]
An expanded metal 20 used as the structure for forming the gas flow passage
16 in the cell 10 is a continuous structure in which a hexagonal mesh 22 shown
in
FIG. 19 is disposed in a so-called zigzag pattern, for example. The expanded
metal
is subjected to a manufacturing process (to be described below) in which slits
are
cut one step at a time in a flat plate-shaped material using a mold while
feeding the
15 material in order to form the mesh 22, whereby each mesh 22 forms a
continuous
staircase-shaped structure in a (materials) forwarding direction (to be
referred to in the
present invention as an "FD direction").
The mesh 22 constituted by the expanded metal 20 is then disposed in the cell
10 shown in FIG. 18 between the gas diffusion layer 14 and the separator 18 so
as to
20 form an inclined surface, whereby triangular gas flow passages 24,
indicated by a
shaded portion in FIG. 20, are formed in a zigzag pattern between the zigzag
mesh 22
and respective surfaces of the gas diffusion layer 14 and separator 18. As a
result,
gas flowing through the gas flow passage 16 flows in the FD direction in
sequence
through the triangular gas flow passages 24 formed in a zigzag pattern. At
this time,
as shown in FIG. 19, a gas flow GF oscillates in the FD direction and an
orthogonal
direction thereto (a transverse direction or a tool direction, to be referred
to in the
present invention as a "tool forwarding direction" or a "TD direction"), and
thus the
gas flow GF flows while making extremely narrow turns repeatedly.
[0006]
When the gas flow GF through the gas flow passage 16 makes extremely
narrow turns repeatedly in the manner shown in FIG. 19, pressure loss in the
gas
flowing through the gas flow passage 16 increases. Therefore, to secure a
required
gas flow, requirements for performance of an air compressor, a hydrogen
circulation
pump, and so on must necessarily become high, leading to an increase in the
size of
CA 02696832 2010-03-03
3
these accessories and a corresponding increase in the size of the fuel cell
system.
Furthermore, the triangular gas flow passages 24 disposed in a zigzag pattern
also
serve as discharge paths for generated water generated in the cell, but the
gas flow
passages according to this constitution have a small passage sectional area,
and it is
therefore difficult to discharge generated water from the cell smoothly. As a
result, a
diffusion overvoltage increases, leading to a reduction in output and a
reduction in
voltage stability.
To ensure that the generated water is discharged smoothly, a drainage
performance may be improved by increasing a gas flow velocity toward a flow
passage outlet (see "Patent Document 2" cited above), but since pressure loss
in the
triangular gas flow passages 24 disposed in a zigzag pattern occurs uniformly
over the
entire gas flow passage 16 and the flow velocity of the gas through the gas
flow
passage 16 is constant, the gas flow velocity remains more or less constant
over the
entire flow passage 16.
The present invention has been designed in consideration of the problems
described above, and it is an object of the present invention to reduce
pressure loss in
a gas flowing through a gas flow passage of a cell as required such that a gas
flow can
be increased appropriately, the size of a fuel cell system can be reduced, an
output of
the system can be increased, voltage stability can be secured, and so on.
Means for solving the Problem
[0007]
To solve the problems described above, a fuel cell according to the present
invention is a fuel cell having a cell structure in which a gas flow passage
is formed
by an expanded metal disposed between cell constitutional members, wherein gas
pressure loss between cell constitutional members can be controlled
appropriately by
modifying a mesh shape of an expanded metal.
(Forms of the invention)
The following forms of the invention illustrate examples of the constitution
of
the present invention, and are itemized to facilitate comprehension of the
various
constitutions of the present invention. The respective items do not limit the
technical
scope of the present invention, and the technical scope of the present
invention may
include configurations in which the constitutional elements of each item are
partially
replaced, omitted, or supplemented by additional constitutional elements while
taking
into consideration the best modes for carrying out the invention.
CA 02696832 2011-12-08
4
[0008]
(1) In a fuel cell having a cell structure in which a gas flow passage is
formed by an
expanded metal disposed between cell constitutional members, a bond portion
connecting a mesh of the expanded metal stands partially upright in a position
where a
bond length is shortened so as to form a part of a strand portion.
In the fuel cell according to this item, the bond portion connecting the mesh
of
the expanded metal stands partially upright in a position where the bond
length is
shortened so as to form a part of the strand portion. Hence, in an opening
formed by
the mesh of the expanded metal, a surface area on which front and rear
openings
overlap in a TD direction increases from an FD direction. Thus, a sectional
area of a
plurality of substantially channel-shaped gas flow passages constituted by a
continuum
in the FD direction of the openings overlapping in the TD direction increases.
As a
result, gas flows through the gas flow passage formed by the expanded metal
disposed
between the cell constitutional members without making repeated narrow turns,
leading
to a reduction in gas pressure loss.
[0009]
(2) In a fuel cell having a cell structure in which a gas flow passage is
formed by an
expanded metal disposed between cell constitutional members, a part of a
strand
portion constituting a mesh of the expanded metal is formed as a continuous
surface not
having a step relative to a bond portion.
In the fuel cell according to this item, a part of the strand portion
constituting the
mesh of the expanded metal is formed as a continuous surface not having a step
relative
to the bond portion. Hence, in the opening formed by the mesh of the expanded
metal,
the surface area on which the front and rear openings overlap in the TD
direction
increases from the FD direction. Thus, the sectional area of the plurality of
substantially channel-shaped gas flow passages constituted by the continuum in
the FD
direction of the openings overlapping in the TD direction increases. As a
result, gas
flows through the gas flow passage formed by the expanded metal disposed
between
the cell constitutional members without making repeated narrow turns, leading
to a
reduction in gas pressure loss.
[0010]
(3) In the fuel cell according to items (1) and (2), a shape of an opening
formed by
the mesh of the expanded metal is basically hexagonal when seen from a step
width
direction of the mesh, and becomes polygonal when one trapezoid formed by
halving
CA 02696832 2011-12-08
the hexagon along a diagonal of a TD direction is shifted relative to the
other trapezoid
in the TD direction.
In the fuel cell according to this item, the bond portion connecting the mesh
of
the expanded metal stands partially upright in a position where the bond
length is
5 shortened so as to form a part of the strand portion, or a part of the
strand portion
constituting the mesh of the expanded metal is formed as a continuous surface
not
having a step relative to the bond portion, and therefore the shape of the
opening
formed by the mesh of the expanded metal is basically hexagonal when seen from
the
step width direction of the mesh, and becomes polygonal when one trapezoid
formed
by halving the hexagon along the diagonal of the tool forwarding direction is
shifted
relative to the other trapezoid in the tool forwarding direction. Hence, the
TD
direction width of the opening shape when seen from the FD direction is larger
than that
of the basic hexagon, and the surface area on which the front and rear
openings overlap
in the TD direction increases from the FD direction. Thus, the sectional area
of the
plurality of substantially channel-shaped gas flow passages constituted by the
continuum in the FD direction of the openings overlapping in the TD direction
increases. As a result, gas flows through the gas flow passage formed by the
expanded
metal disposed between the cell constitutional members without making repeated
narrow turns, leading to a reduction in gas pressure loss.
Note that as a shift amount by which one of the trapezoids formed by halving
the hexagon along the diagonal of the TD direction is shifted relative to the
other
trapezoid in the TD direction increases, the surface area by which the front
and rear
openings overlap in the TD direction increases from the FD direction, leading
to an
increase in the sectional area of the plurality of substantially channel-
shaped gas flow
passages constituted by the continuum in the FD direction of the openings
overlapping
in the TD direction.
[0011]
(4) In a fuel cell having a cell structure in which a gas flow passage is
formed by an
expanded metal disposed between cell constitutional members, an opening shape
of the
expanded metal is basically hexagonal when seen from a step width direction of
the
mesh, and becomes polygonal when one trapezoid formed by halving the hexagon
along a diagonal of a TD direction is shifted relative to the other trapezoid
in the TD
direction.
CA 02696832 2011-12-08
6
In the fuel cell according to this item, the shape of the opening formed by
the
mesh of the expanded metal is basically hexagonal when seen from the step
width
direction of the mesh (also referred to as a "WD direction" hereafter), and
becomes a
polygonal shape when one trapezoid formed by halving the hexagon along a
diagonal
of the TD direction is shifted relative to the other trapezoid in the TD
direction.
Hence, the TD direction width of the opening shape when seen from the FD
direction is
larger than that of the basic hexagon, and the surface area on which the front
and rear
openings overlap in the TD direction increases from the FD direction. Thus,
the
sectional area of the plurality of substantially channel-shaped gas flow
passages
constituted by the continuum in the FD direction of the openings overlapping
in the TD
direction increases. As a result, gas flows through the gas flow passage
formed by the
expanded metal disposed between the cell constitutional members without making
repeated narrow turns, leading to a reduction in gas pressure loss.
[0012]
(5) In the fuel cell according to items (3) and (4), a direction in which one
of the
trapezoids formed by halving the hexagon of the opening formed by the mesh of
the
expanded metal along the diagonal of the TD direction is shifted relative to
the other
trapezoid is shifted in an identical TD direction over a plurality of openings
arranged in
an FD direction.
In the fuel cell according to this item, the direction in which one of the
trapezoids formed by halving the hexagon of the opening formed by the mesh of
the
expanded metal along the diagonal of the TD direction is shifted relative to
the other
trapezoid is shifted in an identical TD direction over a plurality of openings
arranged in
the FD direction, and therefore the plurality of substantially channel-shaped
gas flow
passages constituted by the continuum in the FD direction of the openings
overlapping
in the TD direction are formed as flow passages oriented in an identical TD
direction
over the plurality of openings arranged in the FD direction. In other words,
the gas
flow forms an FD direction flow that deviates toward an identical TD direction
without
meandering while flowing through the plurality of openings shifted in an
identical TD
direction, and as a result, a reduction in gas pressure loss can be achieved.
When the
shift direction is modified, the gas flow turns in the opposite TD direction
in the
modification position and then forms an FD direction flow that deviates toward
an
identical TD direction without meandering while flowing through the plurality
of
openings shifted in an identical TD direction. Thus, the position (timing) in
which the
CA 02696832 2011-12-08
7
flow direction of the gas flow turns is adjusted appropriately in accordance
with the
number in the FD direction of the openings shifted in an identical TD
direction.
[0013]
(6) In the fuel cell according to item (5), a continuous number in the FD
direction of
the openings shifted in the identical TD direction differs in each location or
region of
the expanded metal.
In the fuel cell according to this item, the continuous number in the FD
direction
of the openings shifted in an identical TD direction differs in each location
or region of
the expanded metal, and therefore the gas flow (turn frequency, flow velocity,
gas
pressure loss, and so on) can be adjusted appropriately in each location (a
small spot) or
region (an area having a comparatively large range) of a single cell.
[0014]
(7) In the fuel cell according to items (3) to (6), a shift amount by which
one of the
trapezoids formed by halving the hexagon of the opening formed by the mesh of
the
expanded metal along the diagonal of the TD direction is shifted relative to
the other
trapezoid in the TD direction differs in each location or region of the
expanded metal.
As described above in item (3), as the shift amount by which one of the
trapezoids formed by halving the hexagon along the diagonal of the TD
direction is
shifted relative to the other trapezoid in the TD direction increases, the
surface area by
which the front and rear openings overlap in the TD direction increases from
the FD
direction, leading to an increase in the sectional area of the plurality of
substantially
channel-shaped gas flow passages constituted by the continuum in the FD
direction of
the openings overlapping in the TD direction. Hence, in the fuel cell
according to this
item, by causing the shift amount by which one of the trapezoids formed by
halving the
hexagon of the opening formed by the mesh of the expanded metal along the
diagonal
of the TD direction is shifted relative to the other trapezoid in the TD
direction to differ
in each location or region of the expanded metal, the gas flow (flow velocity,
gas
pressure loss, and so on) can be adjusted appropriately in each location or
region of a
single cell.
[0015]
(8) In the fuel cell according to items (3) to (7), all of the openings formed
by the
mesh of the expanded metal are polygonal when seen from the WD direction.
In the fuel cell according to this item, all of the openings are polygonal
when
seen from the WD direction, and therefore the TD direction width when seen
from the
CA 02696832 2011-12-08
8
FD direction is larger than that of the basic hexagon, and the surface area on
which the
front and rear openings overlap in the TD direction increases from the FD
direction.
Thus, the sectional area of the plurality of substantially channel-shaped gas
flow
passages constituted by the continuum in the FD direction of the openings
overlapping
in the TD direction increases. As a result, gas flows through the entire
region of the
gas flow passage formed by the expanded metal disposed between the cell
constitutional members without making repeated narrow turns, leading to a
reduction in
gas pressure loss.
[0016]
(9) The fuel cell according to items (3) to (7) includes a location or region
in which
the shift amount by which one of the trapezoids formed by halving the hexagon
of the
opening formed by the mesh of the expanded metal along the diagonal of the TD
direction is shifted relative to the other trapezoid in the TD direction is
either zero or
smaller than the shift amount in another location or region adjacent thereto
in the FD
direction.
In the fuel cell according to this item, in the location or region in which
the shift
amount by which one of the trapezoids formed by halving the hexagon of the
opening
formed by the mesh of the expanded metal along a diagonal of the TD direction
is
shifted relative to the other trapezoid in the TD direction is either zero
(when zero, the
opening takes the basic hexagonal shape) or smaller than that of other
locations or
regions adjacent thereto in the FD direction, the sectional area of the
plurality of
substantially channel-shaped gas flow passages constituted by the continuum in
the FD
direction of the openings overlapping in the TD direction is partially
reduced. As a
result, the gas flow flowing through the gas flow passage formed by the
expanded metal
disposed between the cell constitutional members is partially throttled such
that a part
of generated water flowing toward a gas flow passage outlet diverges in the TD
direction. The generated water flowing through the plurality of substantially
channel-shaped gas flow passages disposed in parallel then comes into contact
such that
a single water flow is formed by mutual surface tension, and as a result,
water discharge
through another gas flow passage is promoted. Hence, an increase in gas
pressure loss
due to residual generated water can be suppressed.
[0017]
(10) In the fuel cell according to item (9), the continuum in the shift
direction of the
openings shifted in the identical TD direction is interrupted on either side
of the
CA 02696832 2011-12-08
9
location or region in which the shift amount by which one of the trapezoids
formed by
halving the hexagon of the opening formed by the mesh of the expanded metal
along
the diagonal of the TD direction is shifted relative to the other trapezoid in
the TD
direction is either zero or smaller than the shift amount in another location
or region
adjacent thereto in the FD direction.
By constructing the fuel cell according to this item in this manner, an elbow
portion or a crank portion is partially formed in the plurality of
substantially
channel-shaped gas flow passages constituted by the continuum in the FD
direction of
the openings overlapping in the TD direction. As a result, the gas flow
flowing
through the gas flow passages formed by the expanded metal disposed between
the cell
constitutional members partially curves or meanders in the elbow portion or
crank
portion such that a part of the gas flow diverges in the TD direction, causing
a part of
the generated water flowing toward the gas flow passage outlet to diverge in
the TD
direction. The generated water flowing through the plurality of substantially
channel-shaped gas flow passages disposed in parallel then comes into contact
such that
a single water flow is formed by mutual surface tension, and as a result,
water discharge
through the gas flow passage is promoted. Hence, an increase in gas pressure
loss due
to residual generated water can be suppressed.
[0018]
(11) In the fuel cell according to items (5) to (10), at least one of a
continuous
number in the FD direction of the openings shifted in the identical TD
direction, the
shift amount by which one of the trapezoids formed by halving the hexagon of
the
opening formed by the mesh of the expanded metal along the diagonal of the TD
direction is shifted relative to the other trapezoid in the TD direction, and
the location or
region in which the shift amount is either zero or smaller than the shift
amount in
another location or region adjacent thereto in the FD direction, is varied in
each of a
plurality of stacked cells.
In the fuel cell according to this item, at least one of the continuous number
in
the materials forwarding direction of the openings shifted in an identical TD
direction,
the shift amount by which one of the trapezoids formed by halving the hexagon
of the
opening formed by the mesh of the expanded metal along the diagonal of the TD
direction is shifted relative to the other trapezoid in the TD direction, and
the location or
region in which the shift amount is either zero or smaller than the shift
amount in
another location or region adjacent thereto in the FD direction, is varied in
each of the
CA 02696832 2011-12-08
plurality of stacked cells, and therefore the gas flow can be adjusted
appropriately to an
optimum gas flow in each cell.
[0019]
(12) In items (1) to (11), at least one of a step width and a step depth of
the mesh of
5 the expanded metal differs in the FD direction while an overall thickness
thereof is
fixed in the FD direction.
As will be described below, the expanded metal used as a structure for forming
the gas flow passages in the cell is manufactured through a process in which a
mesh is
formed by inserting slits into a flat plate material one step at a time using
a mold while
10 feeding the material, and therefore the strand width of the mesh increases
as the step
width of the mesh increases. Hence, in the fuel cell according to this item,
at least one
of the step width and the step depth of the mesh of the expanded metal is
varied in the
FD direction while an overall thickness thereof is fixed in the FD direction,
and as a
result, in a location or region in which the step width of the mesh is large,
an opening
length per mesh is large (the mesh is coarse) when seen from the FD direction.
In a
location or region in which the step width of the mesh is small, on the other
hand, the
opening length per mesh is short (the mesh is fine) when seen from the FD
direction.
Hence, in a location or region where the step width of the mesh is large, the
gas flows
while making wide turns, whereas in a location or region where the step width
of the
mesh is small, the gas flows while making narrow turns. Thus, the position
(timing) in
which the flow direction of the gas flow turns can be adjusted appropriately
in
accordance with the step width of the mesh.
Effects of the Invention
[0020]
By constituting the present invention in the manner described above, pressure
loss in the gas flowing through the gas flow passage of the cell can be
reduced as
required, leading to an appropriate increase in the gas flow rate, a reduction
in the size
CA 02696832 2010-03-03
11
of the fuel cell system, an increase in the output of the system, voltage
stability, and
so on.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
FIG. 1 is an illustrative view showing the structure of an expanded metal
serving as a gas flow passage formation member in a fuel cell according to a
first
embodiment of the present invention, wherein FIG. 1A is a view showing the
expanded metal according to the first embodiment of the present invention in a
step
width direction of a mesh, and FIG. 1 B is a view showing a hexagonal expanded
metal serving as a basis of the expanded metal shown in FIG. 1 A from the step
width
direction of the mesh;
FIGS. 2A to 2C show variations of an opening shape of the expanded metal
according to the first embodiment of the present invention;
FIGS. 3A to 3C are perspective views of the expanded metal shown in FIGS.
2A to 2C;
FIG. 4 is a perspective pattern diagram showing a mold of a manufacturing
device for manufacturing the expanded metal according to the first embodiment
of the
present invention;
FIG. 5 is a schematic side view showing the mold and a roller of the
manufacturing device for manufacturing the expanded metal according to the
first
embodiment of the present invention;
FIG. 6 is a schematic side view showing a rolling roller of the manufacturing
device for manufacturing the expanded metal according to the first embodiment
of the
present invention;
FIG. 7 is an illustrative view showing a shift operation for shifting an upper
mold of the manufacturing mold for manufacturing the expanded metal according
to
the first embodiment of the present invention in a TD direction and showing
the
expanded metal from the step width direction, wherein FIG. 7A shows an
operation of
the upper mold for molding the expanded metal according to the first
embodiment of
the present invention, and FIG. 7B shows an operation of the upper mold for
molding
the hexagonal expanded metal that serves as the basis of the expanded metal
according to the first embodiment of the present invention;
CA 02696832 2010-03-03
12
FIG. 8 is a pattern diagram showing a fuel cell including the expanded metal
according to the first embodiment of the present invention, in which a number
of
continuous formations formed during continuous feeding in an identical TD
direction
is varied in each location or region;
FIG. 9 is a pattern diagram showing an example of a manufacturing process
for manufacturing the expanded metal according to the first embodiment of the
present invention in which a step width is varied gradually such that the step
width in
a region close to a gas flow inlet of a cell is narrow, the step width in a
region close to
the gas flow outlet is wide, and the step width in an intermediate region
between the
gas flow inlet and the gas flow outlet is an intermediate width, wherein FIG.
9A
shows a lathe cut metal and FIG. 9B shows an expanded metal obtained by
rolling the
lathe cut metal;
FIG. 10 is a pattern diagram of a fuel cell stack according to the first
embodiment of the present invention;
FIG. 11 is an image diagram of a gas flow passage formed in a fuel cell by the
expanded metal, wherein FIG. 11 A shows a gas flow passage according to the
first
embodiment of the present invention, and FIG. I 1 B shows a gas flow passage
formed
by the hexagonal expanded metal serving as the basis of the expanded metal
according to the first embodiment of the present invention;
FIG. 12 is a graph showing a relationship between a gas flow rate during
power generation and gas pressure loss during power generation corresponding
to
different shift amounts by which one trapezoid formed by halving a hexagon
serving
as a basic opening shape of the expanded metal according to the first
embodiment of
the present invention along a diagonal of the TD direction is shifted relative
to the
other trapezoid in the TD direction;
FIG. 13 is a plan view of a cell including an expanded metal serving as a gas
flow passage formation member of a fuel cell according to a second embodiment
of
the present invention;
FIG. 14 is a partial perspective view showing the expanded metal serving as
the gas flow passage formation member of the fuel cell according to the second
embodiment of the present invention;
FIG. 15A shows a generated water flow through the gas flow passage formed
by the expanded metal shown in FIG. 14, and FIG. 15B shows, as a comparative
CA 02696832 2010-03-03
13
example, a generated water flow that can be generated in the gas flow passage
formed
by the expanded metal according to the first embodiment of the present
invention;
FIG. 16 is a partial perspective view showing an application example of the
expanded metal serving as the gas flow passage formation member of the fuel
cell
according to the second embodiment of the present invention;
FIG. 17 is an illustrative view showing respective parts of the expanded
metal,
wherein FIG. 17A is a plan view of a rhomboid mesh, FIG. 17B is a sectional
view
taken along an A-A line and an A'-A' line, and FIG. 17C is a plan view of a
hexagonal mesh;
FIG. 18 is a sectional view showing an example of a cell structure in a
conventional polymer electrolyte fuel cell;
FIG. 19 is a view showing an expanded metal constituted by a hexagonal
mesh, which is used to form a gas flow passage in the cell shown in FIG. 18,
from a
step width direction of the mesh;
FIG. 20 is a sectional view showing a gas flow passage of a conventional cell,
employing the expanded metal shown in FIG. 19; and
FIG. 21 is a reference diagram showing the respective structures of the
expanded metals for forming gas flow passages in the fuel cells according to
the
related art and the first embodiment of the present invention, wherein FIG. 21
A is a
three-dimensional view corresponding to FIG. 1 A, and FIG. 21B is a
three-dimensional view corresponding to FIG. 1B.
BEST MODES FOR CARRYING OUT THE INVENTION
[0022]
Embodiments of the present invention will be described below on the basis of
the attached drawings. Note that parts which are identical to or correspond to
the
related art will not be described in detail.
First, to describe the embodiments of the present invention, the names of
respective parts of an expanded metal will be clarified with reference to FIG.
17.
The expanded metal is typically a continuous structure in which the hexagonal
mesh
22 described above (see FIG. 19 and FIG. 17C) and a rhomboid mesh 26 such as
that
shown in FIG. 17A are disposed in a so-called zigzag arrangement. An
intersection
portion of the mesh will be referred to as a bond portion BO, and a part that
connects
the bond portions BO of the mesh will be referred to as a strand portion ST. A
CA 02696832 2010-03-03
14
length of the bond portion BO in the TD direction will be referred to as a
bond length
BOI, and a thickness of the strand portion ST will be referred to as a step
width
(forwarding width) W. In the drawing, a reference symbol t denotes a plate
thickness of a material, and a reference symbol D denotes a total thickness of
the
expanded metal. Note that FIG. 17 shows the FD direction (materials forwarding
direction), the TD direction (tool forwarding direction) and the WD direction
(the
mesh step width direction) together.
As is evident from these names, the hexagonal mesh 22 takes a mesh shape in
which the bond portion BO is long, while the rhomboid mesh 26 takes a mesh
shape
in which the bond portion BO is short. An FD direction sectional shape (A-A
sectional shape) of the rhomboid mesh 26 is identical to an FD direction
sectional
shape (A'-A' sectional shape) of the hexagonal mesh 22, and therefore FIG. 17B
shows both FD direction sectional shapes.
[0023]
In a fuel cell according to a first embodiment of the present invention, an
expanded metal is used as a gas flow passage formation member, and FIG. 1
shows an
outline of the structural features of the expanded metal. More specifically,
the bond
portion BO connecting the mesh partially stands upright in positions where the
bond
length BOl (see FIG. 17) is shortened, thereby forming a part of the strand
portion ST.
In other words, a part of the strand portion ST constituting the mesh of the
expanded
metal is formed as a continuous surface not having a step relative to the bond
portion
BO.
Further, in an expanded metal 28 according to the first embodiment of the
present invention, the shape of an opening 30 of the expanded metal is
basically
hexagonal shown in FIG. 1 B and FIG. 21 B when seen from the WD direction, but
when one trapezoid formed by halving the hexagon along a diagonal TDd of the
TD
direction is shifted relative to the other trapezoid in the TD direction, the
hexagonal
shape becomes a polygonal shape (an octagon in the illustrated example), as
shown in
FIG. IA.
[0024]
Further, as shown in FIG. 1A, in the opening 30 formed by the mesh of the
expanded metal 28 according to the first embodiment of the present invention,
the
direction in which one trapezoid formed by halving the hexagon along the
diagonal
TDd of the TD direction is shifted relative to the other trapezoid is shifted
in an
CA 02696832 2010-03-03
identical TD direction over a plurality of openings arranged in the materials
forwarding direction FD.
More specifically, in the example of FIG. 1 A, an opening indicated by a
reference symbol 30L is formed by shifting to the left an illustrated upper
half of the
5 trapezoids formed by halving the hexagon along the diagonal TDd of the TD
direction
relative to a lower half in the TD direction such that three continuous
openings 30L
are formed in the FD direction. Further, an opening indicated by a reference
symbol
30R is formed by shifting to the right an illustrated upper half of the
trapezoids
formed by halving the hexagon along the diagonal TDd of the TD direction
relative to
10 a lower half in the TD direction such that three continuous openings 30R
are formed
in the FD direction.
[0025]
Further, as shown in FIGS. 2 and 3, the shape of the opening 30 formed by the
mesh of the expanded metal 28 may be varied appropriately by modifying the
shift
15 amount by which one of the trapezoids formed by halving the hexagon along
the
diagonal TDd of the TD direction is shifted relative to the other trapezoid in
the TD
direction.
More specifically, FIG. 2A shows an example in which the TD direction shift
amount is set at a maximum allowable shift amount such that the bond length
BOl of
the bond portion BO takes a minimum bond length at which a required strength
can
be secured in the bond portion BO, and FIG. 3A is a three-dimensional pattern
diagram corresponding to FIG. 2A. Further, FIG. 2B shows an example in which
the
TD direction shift amount is set such that the bond length BOl is half that of
the bond
portion BO of the basic hexagon, and FIG. 3B is a three-dimensional pattern
diagram
corresponding to FIG. 2B. Furthermore, FIG. 2C shows an example in which the
TD direction shift amount is reduced such that the bond length BOl is slightly
shorter
than the bond length of the bond portion BO of the basic hexagon, and FIG. 3C
is a
three-dimensional pattern diagram corresponding to FIG. 2C.
[0026]
Referring to FIGS. 4 to 7, a procedure for manufacturing the expanded metal
28 according to the first embodiment of the present invention will now be
described.
A manufacturing device for manufacturing the expanded metal 28 includes a
mold having a die 32, an upper blade 34 and a lower receiving blade 36, and a
roller
for feeding a flat plate material 38 in the FD direction, as shown in FIGS. 4
and 5.
CA 02696832 2010-03-03
16
The upper blade 34 shifts in the TD direction (which is orthogonal to the FD
direction) and rises/falls in the WD direction (up-down direction). Trapezoid
projections 34a are formed on a lower surface of the upper blade 34 at fixed
intervals
in the TD direction.
The flat plate material 38 is fed into the mold by the roller 40 at a
predetermined step width W, and the flat plate material 38 is partially
sheared by the
trapezoid projections 34a and the die 32 and sandwiched between the upper
blade 34
and the lower receiving blade 36. As a result, trapezoid raised cutouts are
formed in
the flat plate material 38. Further, the upper blade 34 is shifted in the TD
direction
every time the upper blade 34 rises such that the trapezoid raised cutouts are
formed
one step at a time in a zigzag pattern, and as a result, a lathe cut metal 28'
having a
staircase-shaped mesh is formed. The lathe cut metal 28' having the
staircase-shaped mesh is then rolled by a rolling roller 42 shown in FIG. 6,
whereby
the expanded metal 28 is formed with the required total thickness D (see FIG.
17B).
[0027]
When the flat plate material 38 is fed into the mold by the roller 40 at the
predetermined step width W and the trapezoid raised cutouts are formed one
step at a
time in the flat plate material 38 by shifting the upper blade 34 in the TD
direction
every time the upper blade 34 is raised and lowered, the opening of the
expanded
metal 28 (the lathe cut metal 28') is formed into the basic hexagonal shape by
causing
the upper blade 34 to perform an alternating reciprocating shift operation in
the TD
direction at half a pitch P of the disposal intervals of the trapezoid
projections 34a
formed on the upper blade 34, as indicated by circled numerals 1-2-1-2 in FIG.
7B.
However, in the first embodiment of the present invention, when the flat plate
material 38 is fed into the mold by the roller 40 at the predetermined step
width W
and the upper blade 34 is shifted in the TD direction every time the upper
blade 34 is
raised and lowered, the expanded metal 28 having the polygonal openings 30
shown
in FIGS. 1 to 3 may be manufactured by performing a shift operation to
continuously
shift the upper blade 34 in an identical TD direction and then continuously
returning
the upper blade 34 in the opposite TD direction at a pitch (1/3P in the
example in the
drawing) that is divided further from half the pitch P of the disposal
intervals of the
trapezoid projections 34a formed on the upper blade 34, as indicated by
circled
numerals 1-2-3-4-3-2-1 in FIG. 7A.
[0028]
CA 02696832 2010-03-03
17
Further, in the expanded metal manufacturing device, the number of
continuous formations formed during continuous feeding in the identical TD
direction
may be varied in each location or region of the expanded metal by modifying a
TD
direction shift control logic of the upper blade 34, as shown in FIG. 8. Note
that in
the example shown in FIG. 8, the number of continuous formations in a region
R1
near a gas flow inlet of the cell is large (using the example shown in FIG.
7A, the shift
operation of the upper blade 34 in the TD direction is set at 1-2-3-4-5-6-5-4-
3-2-1),
the number of continuous formations in a region R3 near a gas flow outlet is
small
(1-2-3-2-1), and the number of continuous formations in an intermediate region
R2
between the gas flow inlet and the gas flow outlet is an intermediate number
(1-2-3-4-5-4-3-2-1).
[0029]
Further, in the first embodiment of the present invention, at the
manufacturing
stage of the lathe cut metal 28', the flat plate material 38 may be fed into
the mold by
the roller 40 such that the step width of the mesh differs in the FD
direction, thereby
varying the total thickness in the FD direction, and in the rolling process
performed
by the rolling roller 42 shown in FIG. 6, the expanded metal 28 may be molded
such
that the total thickness is constant in the FD direction. For example, as
shown in
FIG. 9A, the lathe cut metal 28' is molded such that at least one of the step
width and
a step depth varies gradually, or in other words such that the step width W in
the
region R1 close to the gas flow inlet of the cell is narrow, the step width W
in the
region R3 close to the gas flow outlet is wide, and the step width W in the
intermediate region R2 between the gas flow inlet and the gas flow outlet
takes an
intermediate width, and the expanded metal 28 shown in FIG. 9B is molded by
rolling
the lathe cut metal 28' such that the total thickness is constant in the FD
direction.
[0030]
Further, in the first embodiment of the present invention, at least one of the
continuous number in the FD direction of the openings shifted in an identical
TD
direction, and a shift amount by which one of the trapezoids formed by halving
the
hexagon of the opening 30 formed by the mesh of the expanded metal 28 along
the
diagonal of the TD direction is shifted relative to the other trapezoid in the
TD
direction, may be varied in each of a plurality of stacked cells. For example,
in a
stack 40 shown in FIG. 10, the continuous number of the openings and the shift
amount in the expanded metal of an end portion cell 1 OE are increased over
the entire
CA 02696832 2010-03-03
18
cell 10E. Note that in FIG. 10, a reference numeral 42 denotes a gas inlet
distributor
of the stack 40 and a reference numeral 44 denotes a gas outlet.
[0031]
According to the first embodiment of the present invention having the
constitution described above, the following actions and effects can be
obtained.
As shown in FIGS. 1 A, 2 and 3, in the fuel cell according to the first
embodiment of the present invention, the bond portion BO connecting the mesh
of the
expanded metal 28 stands partially upright in a position where the bond length
BOl is
shortened, thereby forming a part of the strand portion ST. In other words, a
part of
the strand portion ST constituting the mesh of the expanded metal 28 is molded
as a
continuous surface not having a step relative to the bond portion BO. Hence,
when
the opening 30 formed by the mesh of the expanded metal 28 is viewed in the FD
direction, a surface area on which front and rear openings 30 overlap in the
TD
direction increases, whereby a sectional area of a plurality of substantially
channel-shaped gas flow passages constituted by a continuum in the FD
direction of
the openings overlapping in the TD direction increases.
[0032]
Further, as shown in FIGS. 1A, 2, 3 and 21A, the shape of the opening 30
formed by the mesh of the expanded metal 28 is basically hexagonal when viewed
in
the WD direction, but when one trapezoid formed by halving the hexagon along
the
diagonal TDd (FIG. 1 B) of the TD direction is shifted relative to the other
trapezoid in
the TD direction, the hexagonal shape becomes a polygonal shape. As a result,
the
TD direction width of the opening shape is larger than that of the basic
hexagon when
viewed in the FD direction, and the surface area on which the front and rear
openings
overlap in the TD direction increases when viewed in the FD direction. Hence,
the
sectional area of the plurality of substantially channel-shaped gas flow
passages
constituted by the continuum in the FD direction of the openings overlapping
in the
TD direction increases.
More specifically, as shown by the image diagram in FIG. 11, a gas flow
passage 46PA (FIG. 11 B) of a typical expanded metal 20 in which hexagonal
openings are disposed in a zigzag pattern is formed in a narrow region of a
contact
portion with the gas diffusion layer 14 or the separator 18, whereas gas flow
passages
461 (FIG. 11 A) of the expanded metal 28 according to this embodiment are
formed
widely in the vicinity of the contact portion with the gas diffusion layer 14
or the
CA 02696832 2010-03-03
19
separator 18. Therefore, gas flows through the gas flow passages 461 formed by
the
expanded metal disposed between the cell constitutional members without making
repeated narrow turns, and as a result, a reduction in gas pressure loss can
be
achieved.
[0033]
Furthermore, according to the first embodiment of the present invention, in
the
opening formed by the mesh of the expanded metal, the direction in which one
trapezoid formed by halving the hexagon along the diagonal TDd of the TD
direction
is shifted relative to the other trapezoid is shifted in an identical TD
direction over a
plurality of openings arranged in the FD direction, and therefore the
plurality of
substantially channel-shaped gas flow passages 461 constituted by the
continuum in
the FD direction of the openings overlapping in the TD direction are formed as
FD
direction flow passages that deviate toward an identical TD direction over the
plurality of openings arranged in the FD direction. More specifically, as
shown in
FIG. 1 A, a gas flow GF forms an FD direction flow that deviates toward an
identical
TD direction without meandering while flowing through the plurality of
openings 30
(30R) shifted in the identical TD direction, and as a result, a reduction in
gas pressure
loss can be achieved. When the shift direction is modified, the gas flow GF
turns in
the opposite TD direction in the modification position and then forms an FD
direction
flow that deviates toward an identical TD direction without meandering while
flowing
through the plurality of openings 30 (30L) shifted in the identical TD
direction.
By adjusting the position (timing) in which the flow direction of the gas flow
turns appropriately in accordance with the number in the FD direction of the
openings
shifted in an identical TD direction, gas pressure loss can be suppressed over
the
entire cell, and required performance values of an air compressor, a hydrogen
circulation pump, and so on can be suppressed. Hence, an increase in the size
of
these accessories can be prevented, and as a result, a corresponding increase
in the
size of the fuel cell system can be prevented. Furthermore, when the gas flow
passages 461 function as discharge paths for discharging generated water
generated by
the diffusion layer, a generated water passage area is increased such that the
generated
water is discharged smoothly. As a result, a concentration overvoltage
decreases,
leading to an improvement in output and an increase in voltage stability.
[0034]
CA 02696832 2010-03-03
Further, to ensure that the generated water is discharged smoothly, a gas flow
velocity is preferably increased toward the flow passage outlet, and
therefore, as
shown in FIG. 8, the number of continuous formations in an identical TD
direction in
the region RI close to the gas flow inlet of the cell is increased, the number
of
5 continuous formations in an identical TD direction in the region R3 near the
gas flow
outlet is decreased, and the number of continuous formations in an identical
TD
direction in the intermediate region R2 between the gas flow inlet and the gas
flow
outlet is set at an intermediate number. Thus, the pressure loss of the gas
flow
passage can be varied intentionally, whereby the gas flow velocity in the gas
flow
10 passage 16 can be partially increased as required.
By varying the continuous number in the materials forwarding direction of the
openings shifted in an identical TD direction in desired locations and regions
of the
expanded metal in this manner, the gas flow (turn frequency, flow velocity,
gas
pressure loss, and so on) can be adjusted appropriately in each location or
region of a
15 single cell.
[0035]
Further, according to the first embodiment of the present invention, as the
shift
amount by which one of the trapezoids formed by halving the hexagon along the
diagonal of the TD direction is shifted relative to the other trapezoid in the
TD
20 direction increases, the surface area on which front and rear openings
overlap in the
TD direction increases from the FD direction, leading to an increase in the
sectional
area of the plurality of substantially channel-shaped gas flow passages 461
(see FIG.
11A) constituted by the continuum in the FD direction of the openings
overlapping in
the TD direction. Hence, in the fuel cell according to the first embodiment of
the
present invention, the shift amount by which one of the trapezoids formed by
halving
the hexagon of the opening formed by the mesh of the expanded metal 28 along a
diagonal TDd of the TD direction is shifted relative to the other trapezoid in
the TD
direction can be varied in desired locations or regions of the expanded metal,
and as a
result, the gas flow (flow velocity, gas pressure loss, and so on) can be
adjusted
appropriately in desired locations or regions of a single cell.
Note that FIG. 12 shows a relationship between a gas flow rate GFge during
power generation and a gas pressure loss GPlo during power generation, and the
present inventors have confirmed that the gas pressure loss decreases as the
shift
amount in the TD direction increases (TDB>TDS).
CA 02696832 2010-03-03
21
[0036]
Further, in the fuel cell according to the first embodiment of the present
invention, as shown in FIG. 9, at least one of the step width and step depth
of the
mesh of the expanded metal 28 differs in the FD direction while the overall
thickness
thereof is fixed in the FD direction, and therefore, in the location or region
R3 in
which the step width of the mesh is large, the opening length per mesh is
great (the
mesh is coarse) when seen from the FD direction. In the location or region RI
in
which the step width of the mesh is small, on the other hand, the opening
length per
mesh is short (the mesh is fine) when seen from the FD direction. Hence, in a
location or region where the step width of the mesh is large, the gas flow GF
flows
while making wide turns, whereas in a location or region where the step width
of the
mesh is small, the gas flow GF flows while making narrow turns. Thus, the
position
(timing) in which the flow direction of the gas flow turns can be adjusted
appropriately in accordance with the step width of the mesh, and as a result,
similar
actions and effects to those of the example shown in FIG. 8 can be obtained.
[0037]
Furthermore, in the fuel cell according to the first embodiment of the present
invention, at least one of the continuous number in the FD direction of the
openings
shifted in an identical TD direction and the shift amount by which one of the
trapezoids formed by halving the hexagon of the opening formed by the mesh of
the
expanded metal along the diagonal of the TD direction is shifted relative to
the other
trapezoid in the TD direction is varied in each of the plurality of stacked
cells, and
therefore the gas flow can be adjusted appropriately to an optimum gas flow in
each
cell. For example, in the typical stack 40, it is difficult for the gas to
reach the end
portion cell 1 OE and more difficult to discharge generated water from this
cell than
from other cells, and therefore a cell voltage is likely to decrease
dramatically.
Hence, as shown in FIG. 10, the expanded metal 28 of the end portion cell 1 OE
is
formed in advance such that the gas pressure loss is reduced in accordance
with the
example described above, and in so doing, water discharge from the end portion
cell
is promoted, thereby preventing a reduction in the cell voltage. In other
words, by
forming the expanded metal 28 such that the gas flow (turning frequency, flow
velocity, gas pressure loss, and so on) of each cell is adjusted as required,
an optimum
stack 40 can be constructed. Furthermore, by employing the expanded metal 28
in a
CA 02696832 2010-03-03
22
plurality of end portion cells, not only the end portion cell 1 OE, a more
appropriate
gas flow can be obtained throughout the entire stack 40.
As described above, the basic shape of the opening 30 formed by the mesh is a
hexagon when seen from the WD direction, as shown in FIGS. 1A, 2 and 3, and
the
expanded metal 28 that forms a polygon when one of the trapezoids formed by
halving the hexagon along the diagonal TDd (FIG. 1 B) of the TD direction is
shifted
relative to the other trapezoid in the TD direction may be provided in one or
both of
the anode side/cathode side gas flow passages 16A, 16C. Hence, the structure
of the
employed expanded metal is preferably studied appropriately.
[0038]
Next, a second embodiment of the present invention will be described with
reference to FIGS. 13 to 16. Here, detailed description of parts that are
identical or
correspond to the related art and the first embodiment of the present
invention has
been omitted.
As shown by the plan view in FIG. 13, in a cell 10 according to the second
embodiment of the present invention, a gas flow passage 16 (see FIG. 18) is
constituted by an expanded metal 50 shown as a projection. As shown by the
unit
perspective view in FIG. 14, the expanded metal 50 includes a location or
region 52 in
which the shift amount by which one of the trapezoids formed by halving the
hexagon
of the opening formed by the mesh of the expanded metal along the diagonal of
the
tool forwarding direction is shifted relative to the other trapezoid in the
tool
forwarding direction is zero. The region 52 in which the shift amount is zero
basically corresponds to a location or region in which the opening takes the
basic
hexagonal shape.
[0039]
More specifically, the second embodiment of the present invention includes
the location or region 52 in which the shift amount by which one of the
trapezoids
formed by halving the hexagon of the opening formed by the mesh of the
expanded
metal 50 along the diagonal of the TD direction is shifted relative to the
other
trapezoid in the TD direction is smaller (zero at a minimum, as shown in FIG.
14)
than other locations or regions 55, 56 of the expanded metal 50 adjacent to
the
location or region 52 in the FD direction. This is different from the first
embodiment
of the present invention, in which the openings 30 formed by the mesh 28 of
the
expanded metal 20 are all polygons when seen from the WD direction of the
mesh.
CA 02696832 2010-03-03
23
[0040]
Further, in the second embodiment of the present invention, the continuum in
a shift direction of the openings shifted in an identical TD direction is
interrupted on
either side of the location or region 52 in which the shift amount by which
one of the
trapezoids formed by halving the hexagon of the opening formed by the mesh of
the
expanded metal 50 along the diagonal of the TD direction is shifted relative
to the
other trapezoid in the TD direction is either zero or smaller than that of
locations or
regions 54, 56 adjacent to the location or region 52 in the FD direction. In
other
words, in the example of FIG. 14, the location or region 54 is shifted in the
leftward
TD direction and the location or region 56 is shifted in the rightward TD
direction.
[0041]
With the second embodiment of the present invention constituted as described
above, the following actions and effects can be obtained. As shown in FIG.
15A, in
the location or region 52 in which the shift amount by which one of the
trapezoids
formed by halving the hexagon of the opening formed by the mesh of the
expanded
metal 50 along the diagonal of the TD direction is shifted relative to the
other
trapezoid in the TD direction is smaller than that of other locations or
regions adjacent
thereto in the FD direction, the sectional area of the plurality of
substantially
channel-shaped gas flow passages constituted by the continuum in the FD
direction of
the openings overlapping in the TD direction is partially reduced.
As a result, the gas flow flowing through the gas flow passage 16 (FIG. 18)
formed by the expanded metal 50 is partially throttled such that a part of
generated
water W flowing toward a gas flow passage outlet diverges in the TD direction.
Generated water WI, W2 flowing through the plurality of substantially
channel-shaped gas flow passages disposed in parallel then comes into contact
such
that a single water flow W3 is formed by mutual surface tension, and as a
result, water
discharge through another gas flow passage is promoted. Hence, an increase in
gas
pressure loss due to residual generated water can be suppressed.
[0042]
As a comparative example, FIG. 15B shows the expanded metal 28 according
to the first embodiment of the present invention. Here, the gas flow GF
flowing
through the plurality of substantially channel-shaped gas flow passages
disposed in
parallel forms highly independent flows, and therefore gas or generated water
W is
less likely to be exchanged between adjacent passages or with the separator 18
side
CA 02696832 2010-03-03
24
(FIG. 18) and the GDL 12 side (FIG. 18) than in the second embodiment of the
present invention. This tendency is particularly marked during a low load
operation
of the fuel cell.
Hence, when a situation arises in the first embodiment of the present
invention
in which generated water discharge deviates to a specific gas flow passage
such that
the generated water W remains in another gas flow passage, leading to a
possible
increase in gas pressure loss, discharge of the generated water W can be
promoted in
the second embodiment of the present invention, and as a result, an increase
in gas
pressure loss due to residual generated water can be suppressed.
[0043]
Further, in the location or region 52, the continuum in the shift direction of
the
openings shifted in an identical TD direction is interrupted such that an
elbow portion
or a crank portion is partially formed in the plurality of substantially
channel-shaped
gas flow passages constituted by the continuum in the FD direction of the
openings
overlapping in the TD direction. As a result, the gas flow GF flowing through
the
gas flow passages formed by the expanded metal 50 partially curves or meanders
in
the elbow portion or crank portion such that a part of the gas flow GF
diverges in the
TD direction. Accordingly, a part of the generated water flowing toward the
gas
flow passage outlet also diverges in the TD direction, and as a result, the
effect
described above can be obtained.
Note that in the examples shown in FIGS. 14 and 15A, the locations or regions
54, 56 sandwiching the location or region 52 turn back in the TD direction,
but the
locations or regions 54, 56 do not necessarily have to be constituted in this
fashion
and may both be shifted in an identical TD direction.
[0044]
Further, as shown by a different example in FIG. 16, a location or region 58
that turns back frequently in the TD direction may be formed while keeping the
shift
amount by which one of the trapezoids formed by halving the hexagon of the
opening
formed by the mesh of the expanded metal 50 along the diagonal of the TD
direction
is shifted relative to the other trapezoid in the TD direction constant.
In this case, the continuous number in the FD direction of the openings
shifted
in an identical TD direction, differs in each location or region of the
expanded metal
50, but since the gas flow GF flowing through the gas flow passages formed by
the
expanded metal 50 partially curves or meanders such that a part thereof
diverges in
CA 02696832 2010-03-03
the TD direction, causing a part of the generated water flowing toward the gas
flow
passage outlet to diverge in the TD direction, similar actions and effects to
those
described above can be obtained.
Other actions and effects are similar to those of the first embodiment of the
5 present invention, and therefore detailed description thereof has been
omitted.
Description of Reference Numerals
[0045]
10 cell
l0E end portion cell
10 12 MEA
14, 14A, 14C gas diffusion layer
16, 16A, 16C gas flow passage
18, 18A, 18C separator
20, 28, 50 expanded metal
15 22 hexagonal mesh
24 gas flow passage
opening
stack
52 region in which a shift amount by which one of the trapezoids formed by
20 halving the hexagonal opening of the mesh of the expanded metal along a
diagonal of
a tool forwarding direction is shifted relative to the other trapezoid in the
tool
forwarding direction is zero
W, W1, W2, W3 generated water
